I built a Ziroli Zero last year for a friend. Same problem, model needs lots of weight on the front to balance, so a lot off work went into not adding weight in the rear. I mounted the servos at the firewall and used Dave Brown composite pushrods. They needed to be extended, so I joined them with pieces of 1/4" aluminium tubing. Worked perfect. Bear in mind, if you do elect to use long pushrods over a pull-pull system, the pushrods will need some support along their length.
Central Hobbies, (I think it is), has a good carbon pushrod system, that I used a couple years ago, and it works well also.